Because of the increasing popularity of unrestrained access to broadband services by, for example, portable computing devices, there is an increasing need to extend the range of nodes such as access points associated with wireless networks, including but not limited to WLANs and wireless metropolitan area networks (WMANs) described and specified in the 802.11, 802.16 and 802.20 standards. The effective proliferation of wireless networks depends heavily on sustaining and increasing performance levels as user demands increase.
Performance shortcomings between actual and specified performance levels can be caused by attenuation of the radiation paths of RF signals, which are typically transmitted at frequencies of 2.4 GHz or 5.8 GHz in an operating environment such as an indoor environment. Base or AP to receiver or client ranges are generally less than the coverage range required in a typical home, and may be as little as 10 to 15 meters. Further, in structures having split floor plans, such as ranch style or two story homes, or those constructed of materials capable of attenuating RF signals, areas in which wireless coverage is needed may be physically separated by distances outside of the range of, for example, an 802.11 protocol based system. Attenuation problems may be exacerbated in the presence of interference in the operating band, such as interference from other 2.4 GHz devices or wideband interference with in-band energy. Still further, data rates of devices operating using the above standard wireless protocols are dependent on signal strength. As distances in the area of coverage increase, wireless system performance typically decreases. Lastly, the structure of the protocols themselves may affect the operational range.
One common practice in the mobile wireless industry to increase the range of wireless systems is through the use of repeaters. Other approaches can include distributed base stations to broaden coverage areas or the like. However, many of the approaches are prohibitive from an expense standpoint. In more recent discussions within, for example, the Wi-Mesh Alliance IEEE 802.11 Task Group S, the use of ad hoc or mesh networks, where multiple APs are capable of forming connections to each other when proximity is established, are favored as a way of extending the range of the networks. In the proposed evolution of the 802.11(s) standard for mesh networks, mesh nodes are intended to be compatible with the multiple input multiple output (MIMO) and high data rate (540 Mbps) specifications associated with 802.11(n).
Such systems are already deployed in two-way radio networks such as might be used by local government services. In such systems, multiple hops can be traversed before becoming out of range of a primary AP, that is, an AP having the direct connection to the base station, source provider or the like. The primary disadvantage of such systems is the need for expensive proprietary repeaters that are not likely compatible outside of the proprietary network and that are typically configured to operate in accordance with layer 2 or higher of the Open Systems Interconnect (OSI) layered architecture.
It will be appreciated by those of ordinary skill that operation of a repeater at layers above layer 1, commonly referred to as the physical layer (PHY), can cause significant performance issues when time sensitive data or data associated with high bandwidth applications is being transported by the network. For instance, so-called wireless distribution system (WDS) repeaters operate at layer 2 and with a single transceiver causing delay and throughput performance impact as will be discussed in greater detail hereinafter. Because the WDS repeater receives and transmits packets on the same channel, issues such as congestion and at least a 50% reduction in throughput will result. Still further, since the media access control (MAC) address of the packet is modified in conventional layer 2 or higher operation, security features can be compromised along with a reduction in the overall ease of use.
However, for pure physical layer repeaters, problems and complications can arise in that the random packet nature of typical WLAN protocols provides no defined receive and transmit periods. Further, when a series of repeaters are coupled together to serve a client, delays due to cascaded repeating can cause packet acknowledgements (ACKs) to be delayed. Because of delayed ACKs and because packets from each wireless network node are spontaneously generated and transmitted and are not temporally predictable, undesirable consequences such as packet collisions may occur. Some remedies exist to address such difficulties, such as, for example, collision avoidance and random back-off protocols, which are used to avoid two or more nodes transmitting packets at the same time. Under the 802.11 standard protocol, for example, a distributed coordination function (DCF) or other schemes may be used for collision avoidance. However, as the size of a mesh or other network increases, as measured by, for example, the number of “hops,” the amount of delay associated with each hop and the likelihood of at least some delay in the return of ACKs or the like makes pure physical layer processing for individual repeaters prone to possible error as timeouts may occur before higher layer protocol messages can be transferred back and forth along the repeated network paths.
Known approaches to providing repeaters in WLANs, and specifically to providing 802.11 compliant repeaters designed to span larger areas, include providing repeaters configured as two Access Points (APs) in the same box with an inter-AP routing capability between them, and providing a store and forward repeater (SF Repeater). Both approaches are reflected in commercially available products. While a repeater configured as two APs in a box may be suitable for expensive outdoor wireless networks, such repeaters do not meet the requirements of low cost and small form factor generally associated with consumer product applications. Further, such repeaters are complicated to install and operate and can lead to compromised security.
Conventional consumer oriented SF repeaters are typically provided with configuration software. The consumer oriented repeater is generally a WDS repeater with a single radio frequency (RF) section as opposed to the two AP approach noted above. Such a repeater is loaded with software which determines the channels used by the AP. Channel information is then communicated by the consumer during initial configuration to the SF repeater to configure the repeater in kind. Problems arise however, in that such systems are difficult to implement for the average consumer as they require some basic knowledge, or at least the ability to interpret data values associated with the WLAN parameters.
One system, described in U.S. National Stage application Ser. No. 10/516,327 based on International Application No. PCT/US03/16208, incorporated by reference herein, and commonly owned by the assignee of the present application, resolves many localized transmission and reception problems by providing a repeater which isolates receive and transmit channels using a frequency detection and translation method. The WLAN repeater described therein allows two WLAN units to communicate by translating packets associated with one device at a first frequency channel to a second device using a second frequency channel. Since the repeater operates as a physical layer device, the MAC address of the packets are not modified, as would be the case in a repeater configured as a layer 2 or higher device. The direction associated with the translation or conversion, such as from the first frequency channel associated with the first device to the second frequency channel associated with the second device, or from the second frequency channel to the first frequency channel, depends upon a real time configuration of the repeater and the WLAN environment. For example, the WLAN repeater may be configured to monitor both frequency channels for transmissions and, when a transmission is detected, translate the signal received on the first frequency channel to the other frequency channel, where it is transmitted to the destination. It is important to note that the frequency translating repeater described in application Ser. No. 10/516,327 acts in near real time to receive, boost and retransmit packets. While addressing many of the problems in the art, the frequency translating repeater described in application Ser. No. 10/516,327 lacks capabilities such as store and forward or higher layer intelligence or processing capability, including filtering traffic based on knowledge of network operating conditions. Such a repeater is the equivalent of, for example, a hub for a wireless LAN.
In general, repeaters will be used where the placement of a wired connection to a LAN, such as an Ethernet LAN connection or the like, is undesirable. Where several repeaters can be used to extend LAN ranges, it would be desirable for a physical layer (PHY) repeater that can address the consequences of delay and the like as described above without being prohibitively expensive. It would be further advantageous for a PHY repeater to be capable of treating packets differently based on characteristics of the packet such as a source or destination address or a priority associated with the packet while preserving packet and network security mechanisms.